Autonomous vehicles use various computing systems to aid in the transport of passengers from one location to another. Some autonomous vehicles may require an initial input or continuous input from an operator, such as a pilot, driver, or passenger. Other autonomous systems, for example autopilot systems, may be used only when the system has been engaged, which permits the operator to switch from a manual mode (where the operator exercises a high degree of control over the movement of the vehicle) to an autonomous mode (where the vehicle essentially drives itself) to modes that lie somewhere in between.
Such vehicles are typically equipped with various types of sensors in order to detect objects in the surroundings. For example, autonomous vehicles may include lasers, sonar, radar, cameras, and other devices which scan and record data from the vehicle's surroundings. Sensor data from one or more of these devices may be used to detect objects and their respective characteristics (position, shape, heading, speed, etc.). This detection and identification is a critical function for the safe operation of autonomous vehicle.
In some autonomous driving systems, features such as lane markers are ignored by the autonomous driving system. When the lane markers are ignored, the autonomous vehicle may maneuver itself by relying more heavily on map information and geographic location estimates. This may be less useful in areas where the map information is unavailable, incomplete, or inaccurate.
Some non-real time systems, such as those systems which do not need to process the information and make driving decisions in real time, may use cameras to identify lane markers. For example, map makers may use camera images to identify lane lines. This may involve processing images in order to detect visual road markings such as painted lane boundaries in one or more camera images. However, the quality of camera images is dependent upon the lighting conditions when the image is captured. In addition, the camera images must be projected onto the ground or compared to other images in order to determine the geographic location of objects in the image.